BOSTON – During his first season as an NBA head coach, Brad Stevens’ greatest accomplishment was remaining himself.

Heaven knows he had times when he wanted to flip a chair, punt a basketball or hurl obscenities throughout a postgame press conference, but he left the Boston Celtics' 25-57 season with the same steadiness as when the team introduced him as coach last summer.

Danny Ainge wanted no one else then, and he desires no other leading man now. Stevens is a hoops junkie with an addiction for improvement who dealt with a losing season as well as anyone could have expected.

Did he seamlessly transition from college to the pros? Of course not. Stevens needed to adjust to new rules and better competition – not just the players, but opposing coaches too. These men spend their lives learning Xs and Os. Some of them started in the film room and broke down NBA tapes for years before getting promoted to the bench, only to pull all-nighters for several more years before getting the chance to run their own teams. Others spent 15 years as players learning the ins and outs of the NBA game.

In one summer, Stevens had to take a crash course about a brand new life – the travel, a lack of practices, how to fit in new players acquired midseason, even pregame media sessions, how to drive to the arena and where to go to Dunkin Donuts – that is so different from his former life at Butler. There was only so much he could learn before starting the regular season.

But one unfounded fear was that Stevens might fail to adjust to the NBA culture. People, including some very smart people, wondered whether Stevens could command respect from pros. He arrived amiable and friendly and successful, but a long line of college coaches had failed to connect with players. Not Stevens. Not during year one, at least. He walked into the Waltham practice facility last summer, called himself Rajon Rondo’s biggest fan and immediately began showing a group of Celtics how committed he is to making them better and getting to know them as people.

Again, Stevens was not immediately perfect. But the Celtics did not sign him with the belief that he would instantly become the NBA’s top coach. They knew the learning curve was steep and trusted Stevens would keep pushing even when the setbacks hurt the most. He especially regretted his team’s inability to close out tight games and the defensive slippage that occurred during the last few months, but he took solace in the fact that the locker room never splintered. Keith Bogans’ dismissal aside (and that situation never seemed to cause a rift among the rest of the players), togetherness became Stevens’ proudest accomplishment.

“It starts with Danny Ainge and it starts with Brad Stevens,” Rondo said, “and I think it continued down throughout the locker room.”

As Stevens waited for Wednesday night’s season finale – which became yet another loss – he reflected on something an NBA figure told him when he accepted the Celtics job: “You have a chance to be a good coach. But you’re going to be a lot better in year two.”

What will he do to prepare during the offseason? First he owes his daughter a couple of hours to watch Frozen with her for “the 18,000th time.” But after he takes a little family time he plans to keep working toward the future. Part of that will be reflecting on what went wrong during his rookie season. He has already started exit interviews to help design every players’ offseason workouts. He put a lot of time into those summer plans, started discussing them with the media back in December. He said he will be available to players this summer as much as they want him to be.

The focus has been on development since Stevens walked through the door. He has encouraged Avery Bradley to expand his range and big men to shoot threes and a whole load of other tweaks designed to help tomorrow. The way Stevens sees it, players can either get better within their roles or spend the summer working to expand their roles.

“What I mean by that is: Are you going to get better at what you do well, or are you going to get better at some other things that give you the chance to be the fifth guy instead of the eighth guy, be the third guy instead of the fifth guy,” the coach explained. “We have a lot of great data to be able to share and subjective thoughts as well, and I think we can get better with the guys in the room.”

He wants to get better too. After a full NBA season, he feels comfortable with the new rules, the changes with timeouts, the 24-second shot clock, and the extra minutes that make each game so many more possessions long. He figures he has seen just about every way NBA teams will defend the pick-and-roll. He has game-planned for spread attacks that feature the world’s best athletes. He knows what it’s like to prepare for the second game of a back-to-back on almost no sleep with only a hotel walkthrough to share the scouting report with his players. He's learned so much. But he still sees so much room to grow.

“He’s a special person and a great coach and the players see it,” Ainge said. “The players see his work ethic, they see his integrity and they see his intelligence. So I think he’s earned the respect of the team in a really difficult situation and I know he’s going to get better. He’ll be better next year and he’ll be better the next year. He’s a sponge, and he’s very intelligent with a great work ethic. And I couldn’t be happier.”

Stevens is a sports fanatic. “I don’t know what you all like to watch on TV. I haven’t watched a sitcom, reality show or one of those signing shows all year,” he said. He watches the Red Sox now and he will watch the NBA playoffs “because that’s what I’ve always done and that’s what I like to do.”

“Obviously we’ll have those games all taped. We’ll have access to all those games. We’ll be able to pull those back up, break those down,” he said. “There will be things that I’ll be very interested to see. I’ll probably be watching it more for the adjustments game to game than I have in the past. As far as actions go, as far as how people defend in their base system, you learn those things through 82 games. But just seeing and having an eye on what people are doing game to game – specific to who they have and who they are – will be interesting to watch. Especially after being through this.”

Stevens appeared in two national championship games and became a boy wonder at Butler, but his desire to study playoff adjustments is another sign that he still has a lot left to experience at the NBA level.

The Celtics players were not ignorant to Stevens’ greenness. Earlier this season, Gerald Wallace told the great Jackie MacMullan that the coach “still has some college in him” and drew plays like the NBA used a 35-second shot clock. “Yeah, yeah, you can tell,” Wallace said. “He’s kind of nervous a little bit, but who isn’t?”

“It’s his first year just like mine, Kelly (Olynyk’s) and the other rookies',” Phil Pressey said after the season concluded. “We went through some learning experiences but I feel like he learned the fastest, on the quickest curve.”

This season was not easy. The Celtics were designed for the three Fs: failure, flexibility and the future. Rain kept pelting down from the sky but the organization always trusted that Stevens would do whatever he could to hold onto the umbrella. The Celtics signed him to a six-year contract with the idea that he could learn while the team rebuilt and be ready to prosper by the time Ainge put together a viable roster.

“I think the best thing I learned is that it’s not fun to not win,” Stevens said. “But it doesn’t define who you are and how you go about your business.”

That’s the attitude Ainge always saw in his young coach. For all of Stevens’ intelligence and prior success, it was his unflappable demeanor that allowed him to keep the locker room together during his first year on the job.

So much about this team will change in the coming years. Faces, talent level, expectation. But the Celtics feel they have a foundation in Stevens.

“I have no worries about Brad,” Ainge said. “Brad is maybe the only thing in this whole organization I’m not concerned about.”